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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Crash Risks by Commercial Motor Vehicle (CMV) Driver Schedules


To collect hours-of-service (HOS) and crash data to analyze how HOS provisions are being used and the impact of driver schedules on crash risk.


The Federal Motor Carrier Safety Administration (FMCSA) conducted a study that evaluated the impact of driving hours, working hours,  and breaks on safety critical events (SCEs) (Blanco, M., et. al., 2011). The study included 99 drivers who drove a total of 700,000 miles, during which naturalistic driving video and data were collected. That study found that (1) as the number of driving hours increased, so did the number of SCEs, (2) when evaluating the interaction between driving and non-driving work, a much greater time-on-task effect emerges for drivers driving late in their work shift, and (3) driving breaks decrease risk in the hour after a break.


This study collected additional data to answer important questions related to driver schedules and how these factors impacted overall driver performance and fatigue. This study was designed to be done in phases. In Phase I, the research team collected HOS and crash data. In Phase II, the research team would use the data collected in Phase I to analyze crash risk as it related to various aspects of the HOS provisions.  
This study analyzed:
  • Relative crash risk by hour of driving.
  • Relative crash risk by hour of driving per week.
  • Relative crash risk of driving breaks.
  • Relative crash risk as a function of recovery periods.
  • How each of the HOS provisions was being used.
In addition, the study designed, developed, and delivered a database so that the data collected in this study could be used for future research efforts.


A database of the HOS and crash data for use in future research efforts.


May 2014: Phase I contract awarded
July 2014: Kick-off meeting
October 2014: Peer review meeting
November 2015: Phase I complete


FY 2014: $267,000

Current Status

The first phase of this project is completed.


Virginia Tech Transportation Institute